If the police knock and ask to enter your home, you don’t have to admit them unless they have a warrant signed by a judge. However, in some emergency situations (like when a person is screaming for help inside, or when the police chasing someone) officers are allowed to enter and search your home without a warrant. If you are arrested, the police can search you and the area close by. If you are in a building, “close by” usually means just the room you are in.